Radiological imaging of hydrocephalus.

Dr/ ABD ALLAH NAZEER. MD.

The contrast among a normal brain in a normal adult (left), the brain of a normal man with impressive hydrocephalus and an equally impressive hydrocephalus in a 54-year-old man with deep cognitive and motor impairment since childhood (right;

A 25-week premature male with an intraventricular hemorrhage and subsequent development of hydrocephalus: ( a ) CUS shows the right-sided intraventricular hemorrhage; ( b ) CT also shows parenchymal hemorrhage

Congenital hydrocephalus.

Congenital hydrocephalus.

Congenital hydrocephalus.

A 4-month-old male with vein of Galen malformation: ( a ) MRI shows the dilated vein of Galen; ( b ) cerebral angiogram shows the dilated vein of Galen and the surrounding vasculature

( a – b ) A 8-year-old female with a posterior fossa brain tumor and hydrocephalus.

A 13-year-old male with hydrocephalus secondary to aqueductal stenosis, status post endoscopic third ventriculostomy (ETV). CSF cine flow study demonstrates CSF flow across the fenestration in the anterior third ventricle: ( a ) phase-contrast magnitude cine MRI; ( b ) phase contrast directional cine MRI.

CT/MRI axial scans demonstrating ventriculomegaly with relatively well- identified sulci. Periventricular edema is observed in case 4 which suggest acute onset.

Pineal body tumour with hydrocephalus.

Communicating hydrocephalus.

Communicating hydrocephalus.

Communicating Hydrocephalus.

Aqueductal Stenosis

Tectal Glioma.

Giant cell astrocytoma with hydrocephalus.

Choroid plexus papilloma.

Choroid plexus tumors with hydrocephalus.

Choroid plexus carcinoma with hydrocephalus.

Fourth ventricular medulloblastoma with hydrocephalus.

Fourth ventricle tumour with hydrocephalus.

Posterior fossa immature teratoma with hydrocephalus.

Posterior fossa cystic mass with hydrocephalus.

Tuberculous meningitis with hydrocephalus.

Normal Pressure Hydrocephalus• Described by Hakim, Adams, et al (1965).• 50% known cause (SAH, meningitis).• 50% idiopathic (older).• Diagnosis primarily clinical: Gait apraxia, dementia, incontinence.• Radiology: communicating hydrocephalus.

Physiologic Tests for NPH• Nuclear cisternography– Communicating hydrocephalus• Pressure monitoring– Water hammer pulse– Plateau waves• Saline Infusion (outpatient)– If resistance > 4mmHg/ml/min, 82% respond to ELD• 50 cc Tap test: PPV 73-100%; sensitivity 26-62%• External lumbar drainage (inpatient)

External Lumbar Drainage• 16 gauge lumbar puncture; catheter drainage• 10 cc/hour for 3 days; gait assessed.• Of 151 patients* with iNPH,100 improved with ELD.– Gait only (88%), gait/dementia (84%), triad (59%).• Of responders, 90% improve with VP shunt.• Of nonresponders, 22% improve with shunt.

What Causes Idiopathic NPH?• Consider normal bulk flow of water in brain• Consider association of deep white matter ischemia (DWMI) and NPH.

Normal Bulk Flow of Extracellular Brain Water• Water leaves upstream arterioles under pressure-osmotic gradients (e.g, mannitol).• Normal and excess water resorbed by downstream capillaries and venules.• Vasogenic edema flows centripetally to be absorbed by ventricles• Interstitial edema flows centrifugally to subarachnoid space via extracellular space.

Possible Etiology of NPH• Hypothesis: NPH patients have always had large ventricles (“slightly enlarged”)– Decreased CSF resorption (saline infusion test)– Unrecognized benign external hydrocephalus?• No evidence for previous SAH or meningitis• Significant CSF resorption pathway is via extracellular space of brain (like tectal gliomas)• Everything fine until “second hit”: DWMI

DWMI is “Second Hit” in NPH• No symptoms until DWMI occurs later in life• Resistance to peripheral CSF flow through extracellular space increases slightly due to DWMI.– loss of myelin lipid: more hydrophilic environment– Greater attraction of out flowing CSF to myelin protein• CSF production continues unabated– Accumulates in ventricles -hydrocephalus worsens– Increased tangential shearing forces.– NPH symptoms begin.

NPH.

NPH.

CSF Flow Void.

Proposed Causes of CSF Motion• Production by choroid plexus (500 ml/day).• Cardiac pulsations.– Choroid plexus (Bering, 1959).– Large arteries.– Cerebral hemispheres (phase- contrast MRI).

Normal flow.

Hyperdynamic flow.

Enlarged Sylviancisterns in NPH

Association of DWMI and NPH: Clinical• Some cases of L’etat Lacunaire (Marie, 1901) may have been NPH (Fischer, 1981)• Coexistence of NPH and Hypertensive Cerebrovascular Disease Noted Previously(Earnest 1974, Goto 1977, Graff-Radford 1987)

• CSF flow void is useful indicator of favorable response to CSF diversion• Presence of DWMI is not contraindication to shunting• NPH and DWMI may be related

CSF Flow Measurement• CSF flow void on conventional MR images represents average motion during 256 spin echo acquisitions.• Since CSF motion is due to cardiac pulsations, it is better evaluated using cardiac gated techniques.

Phase Contrast CSF Velocity Imaging• “Velocity” is speed plus direction• Flow sensitization along craniocaudal axis– Flow up: shades of black– Flow down: shades of white– No flow: gray– Set aliasing velocity– Quantification of velocity or flow

Qualitative CSF Velocity Imaging.

Quantitative CSF Flow Study• 512x512; 16 cm FOV• .32 mm pixels• 4mm slice angled perpendicular to aqueduct• Velocity-encode in slice direction• Retrospective cardiac-gating (not EKG triggering)

Through-plane flow-encoding• Venc= 10, 20, 30 cm/sec (NPH)• Venc= 5 cm/sec (shunt malfunction)

Quantitative CSF Velocity Imaging• Calculates “Aqueductal CSF stroke volume”• Stroke volume: microliters of CSF flowing back or forth over cardiac cycle• Verified by pulsatile flow phantom using ultrasound flow meter (Mullin, 1993)

Quantitative CSF Velocity Imaging

CSF Flow Study: No Flow.

Conclusions• NPH diagnosed by symptoms, not MRI• MRI used to confirm diagnosis of shunt-responsive NPH• Asymptomatic patients may have dilatedventricles and elevated CSF flow: Pre NPH?• Not everyone with benign external hydrocephalus gets NPH• Keep your extracellular space open

Thank You.